Hi Galathaea, Why are you posting from both Win_XP and Mac boxen ?

Physicists ( and engineers ) don't need a Swiss Army knife.
You don't use a fork-lift to pick up a pea,
nor do you use a fork to pick up pallet loads.

Quoting from my website, " www.Cotse.NET/users/jeffrelf/ ":

Based on the desired result and " givens ",
scientists chose the best model(s)... be it Quantum Mechanics,
thermodynamics, special relativity, general relativity or a mix.

Like thermodynamics, Quantum Mechanics and the Uncertainty Principle
are about temperatu

An ideal laser is perfectly coherent, at absolute zero.
( But the energy of the wave itself is the proper temperature )

The more coherent your source is
( e.g. a laser, Cooper pairs, etc. ):

1. The less you can know ( in theory and/or practice )
which slit the particle passed though.

2. The more you know, a priori, the momentum, the frequency
and the integrity of the interference pattern.

General Relativity can model the field of a massive object
only because its energy is so very predictable.
" Static 4-D spacetime " ( i.e. GR's gravitational field )
equals, " 8 * pi * G * T_αβ / c^4 ".
( A function of density and pressure )

The metric and the light cone can be " givens ", static.

Geodesics inside the cone are " Timelike ",
geodesics on the surface of the cone are lightlike,
the rest are spacelike.

If you assume the -+++ signature
( i.e. imaginary time, orthogonal to " length " )
timelike signatures are negative.